If you are a returning contributor and already have checkout out the old fedorahosted git repository, then in step 2 of the forking guide instead of cloning the repository you can simply update your current one to point to your new github fork:

git remote set-url origin git@github.com:username/spacewalk.git

--or--

git remote set-url origin https://github.com/username/spacewalk.git

Changes should be made to the to master branch; we'll take care of applying them to other releases as appropriate.